Aluminum-containing particles in synovial fluid of a patient with normal renal function and chondrocalcinosis

A 48-year-old Caucasian woman presented a tender effusion of small volume, with a mild increase in skin temperature in her right knee acid widespread chondrocalcinosis found radiologically. She had normal renal function, had undergone a gastrectomy, and was receiving therapeutic doses of aluminum hy droxide antacids. Synovial fluid analysis showed small, irregular, nonbiref ringent particles that stained intensely positive with the alizarin red sta in. Scanning electron microscopy, energy dispersive X-ray analysis, and mic roprobe analysis showed aluminum and variable concentrations of chlorine an d/or oxygen in isolated small spherical particles (average diameter about 1 5 mu). Neither phosphorus nor calcium was ever detected in the aluminum con taining particles. These findings strongly suggest the presence of a mixtur e of aluminum hydroxide and some form of aluminum hydroxide chloride; neith er was previously reported in synovial fluid of patients with normal renal function. Aluminum-containing particles should be considered an explanation for unexplained particles in joint fluid and may be a factor in some arthr itis.